1. Field of the Invention
The present invention relates generally to shock absorbing padding materials and the like, and more particularly to an improved shock absorbing sheet material having a plurality of small, active pumping elements formed therein including chambers of different sizes interconnected by communicating passageways such that a compressive force applying member engaging the material will first contact a wall forming one of the larger chambers causing it to collapse resiliently and pressurize a connected smaller chamber which expands and is subsequently engaged by the compressing member, and the two thereafter jointly exert resilient resistance to continued compression of the sheet material.
2. Brief Description of the Prior Art
Prior art sheet materials and pads include various types of gas-containing chambers intended to resiliently resist compression of the material and thereby perform shock-absorbing or dampening functions. Examples include bubble-pack packing materials, honeycomb pads, and simple sponge-configured pads such as the type used under carpet. However, in all such materials a compressive force applied thereto will experience a more or less uniform resistance as the resilient material and/or entrained gases are compressed. This causes the material to react in a manner similar to an undamped spring. In many applications, shock absorbing performance could be improved if the reactance of the pad had a non-linear characteristic, that is, if in response to the application of a uniform compressive force the pad resisted in a stepped or non-linear fashion. For example, in the case of shoe sole applications the anatomical impact experienced by the wearer of the shoes could be improved by causing the foot to experience a non-linear deceleration before it bottoms out as the sole reaches maximum compression.